1. Field of the Invention
The present invention relates to a device and process for the sterilization and depyrogenation of dental and surgical metal instruments. The invention relates, more particularly, to an automatically controlled device for the rapid, inexpensive and non-corrosive sterilization and depyrogenation of dental and surgical metal instruments.
2. Description of the Prior Art
In every health profession, the guiding principle ". . . do good, but do no harm" is as valid today as in the ancient Greece of its author, Hippocrates. Over the years, the second part of this motto was directed at the patient while treatment-related hazards to the practitioner's health were either discounted or accepted stoically. In dentistry, the simplistic attitude that patients--not professionals acquire treatment-related diseases is giving way to the more realistic concept that operatory personnel are the main targets of viral and bacterial agents of infections.
To demonstrate the central position of dentists in the acquisition and broadcast of nosocomial infectious disease, their rate of hepatitis B infection is four-fold higher than that of the general public. If the dentist is male, he can pass the disease by sexual activity to his wife. If she, or female operatory personnel, incubate the virus during pregnancy, their newborn children have a 90% chance of becoming lifelong carriers of the virus and a 53% chance of dying from liver cancer. Male or female, dental personnel harboring hepatitis B virus can pass the disease to patients, especially via blood exiting the finger through cuts.
The recent dramatic rise in the spread of infectious diseases in the United States has resulted in an acute awareness of the potentially grave danger of transmission to health care professionals in general. As noted above, dentists and dental auxiliaries occupy a central position in the acquisition and broadcast of nosocomial infectious disease. The risk, however, extends beyond dentists and dental auxiliaries to the crossover contamination from patient to patient.
For example, it is estimated that there are 200,000 new cases of hepatitis B in the U.S. each year with nearly 1 million chronic carriers. Since 1974, there has been a 234% increase in reported cases of Herpes Simplex II and a 40,350% increase in AIDS cases. Add to these the diseases that can frequently be transmitted, such as gonorrhea, infectious mononucleosis, measles, pneumonia, tetanus, amoebic dysentery and the highly resistant organisms that are reaching the United States from foreign countries, and a frightening scenario emerges.
Recent legal decisions have placed the burden of proof of proper sterilization procedures on the dental office where the possibility of suspected transmission of infection exists. It follows that malpractice insurance carriers may soon require strict adherence to effective and accepted sterilization procedures.
The solution to the problem of contamination with infectious disease in the dental office from patient to dental personnel and from patient to patient is to ensure the complete sterilization and depyrogenation (killing all forms of microbial life: viral and bacterial pathogens including spores) of all instruments.
In the dental office environment, there are several currently accepted means of sterilization. All of the systems currently employed, as discussed below, lack the capability of rapid sterilization of instruments between patients to allow the immediate reuse of the instruments.
The first method of sterilization is known as cold solution sterilization. Cold solution sterilization requires 20 to 30 minutes to disinfect and 10 hours to sterilize (if the solution is fresh and mixed to proper strength). Procedural problems involved with cold solution sterilization are as follows: many currently available solutions will discolor the skin on contact; most available solutions have an offensive odor; dental instruments will rust if they are left in the solutions over an extended period of time; and instruments are often placed in the solution haphazardly with no record of how long they remain. Other limitations concerning the cold solution sterilization system include the fact that the required solutions are expensive and must constantly be replenished.
The second method of sterilization involves the utilization of steam heat. Steam heat sterilization requires 30 to 60 minutes to sterilize. Procedural problems involved with steam heat sterilization are as follows: a central sterilization area is required and a large piece of expensive equipment which can be hazardous to operating personnel is required. Other limitations concerning steam heat sterilization include the fact that the method corrodes, rusts and dulls instruments--particularly where such instruments are of a carbon steel construction.
The third method of sterilization involves the use of alcohol steam. Alcohol steam requires a minimum of 30 minutes to achieve sterilization. Procedural problems involved with alcohol steam sterilization are as follows: a central sterilization area is required; sterilization usually requires the use of "wrapped packs" which necessitate an increase in the number of instruments needed by an office; and the use of "wrapped packs" also lends itself to careless techniques in that packs are often broken into to retrieve one needed instrument if complete packs of all instruments are not available. Other limitations concerning alcohol steam sterilization include the fact that alcohol steam also corrodes instruments, but not to the same degree as steam heat. Additionally, alcohol steam contains formaldehyde--the presence of which constitutes a potential health hazard. Accordingly, purging systems are typically required to exhaust the alcohol steam from the sterilizer cabinet each time its access door is opened.
The fourth method of sterilization involves the use of dry heat. Dry heat sterilization conventionally requires a minimum of 60 minutes to achieve sterilization. With the exception of the purging requirements associated with the presence of formaldehyde, the problems involved with dry heat sterilization are essentially the same as discussed with regard to alcohol steam sterilization since wrapped packs are used. Additionally, however, the lack of uniform sterilizing heat distribution, and a corresponding non-uniform temperature pattern within the sterilizing cabinetry, render the validation of the sterilization process somewhat difficult.
The fifth method of sterilization involves the use of ethylene oxide gas. The size, expense and sophistication of this process and the necessary equipment, however, limit its use to commercial large volume sterilization.
The sixth method of sterilization involves the use of heat transfer with glass beads, sand, glass, ball bearings and other similar items being used as a heat-transfer medium. Heat transfer sterilization requires 10 seconds at 450.degree. to achieve sterilization. This method has no known procedural problems. A major limitation concerning heat transfer sterilization, however, is the fact that a small unit is used which is suitable only for small endodontic files, broaches and other similar items.
Among the currently employed sterilization systems, the heat transfer system is the only one with the capability of rapid sterilization of instruments between patients and its small capacity limits its use in the dental office.
Thus, a need exists in the art for a rapid, safe, inexpensive and non-corrosive sterilization method and device that provides for the automatic sterilization and depyrogenation of procedural instruments in health care facilities and especially the dental office thereby minimizing the human error factors attending the use of known sterilization devices.